The name "Plantagenet" has been attributed to many sources. It has been suggested that because Geoffrey of Anjou was accustomed to wearing in his hat a sprig of broom flower (Latin: planta henista), his son adopted that symbol for the dynasty he founded in England. Wearing a broom sprig in the cap was based on the broom's ancient reputation as a plant both "useful to witches and against them as a magic sleep inducer and as a power in love". The Plantagenet Kings claimed they were decended from a witch Milusine who married an early Count of Anjou and then vanished in a puff of smoke when forced to attend Mass. Be that as it may, Henry II. may have been England's first "Plantagenet", but it was not until the time of Richard, Duke of York, that the name was formally adopted in order to help emphasise the Yorkist claim to the throne during the Wars of the Roses.

However, the Founding Ancestor of this family is here taken to be Geoffrey "Ferde", Count of Gastinis (post/ca.1168) who married Ermengard - heiress to her brother Geoffrey Martel of Anjou, the daughter of Fulk III "the Black", Count of Anjou - during the first century of the 2nd Milenium. His grandson Fulk V. (ca.1088-1143) succeeded to the throne of the Crusador Kingdom of Jerusalem, thus established his family's reputation internationally. Some suggest it was he who adopted the name "Plantard" to emphasize his link through his wife to the Merovingians. Henry II., ca.1133-89, 1st "Plantagenet" King of England, was his grandson.